The invention relates to an apparatus for use in spinning preparation for detecting foreign objects of plastics material, such as polypropylene bands, fabric and films and the like, in or among fibre material, especially fibre flocks, for example, of cotton. The fibre material may in particular, but not exclusively, be fibre flocks being removed (opened) from bales of textile fibre, during which process a foreign object detector and the fibre flocks are movable relative to one another, the foreign object detector comprising a transmitter and a receiver for electromagnetic waves or rays and an evaluating device for distinguishing the foreign objects from the fibre flocks.
In a known apparatus (DE 36 44 535 A1), the fibre flocks are arranged in a loose pile on a moving conveyor belt. A transmitter for the electromagnetic waves or rays is arranged above the conveyor belt with the pile of fibre flocks. A receiver is located between the upper and lower belt regions. The material of the conveyor belt is a material that is permeable to electromagnetic waves or rays. The loose pile of flocks is then irradiated. The foreign objects are often polypropylene bands. The apparatus enables the form (shape) colour, size or brightness of foreign objects to be determined. The recognised outwardly differing features of the foreign objects are used to differentiate them, by a comparison process, from the good fibres of the fibre flocks.
It is an aim of the invention further to improve the apparatus for detecting foreign objects of plastics materials, such as polypropylene bands, fabric and films, and the like.